U.S. patent number 8,089,190 [Application Number 12/620,748] was granted by the patent office on 2012-01-03 for rotor for an interior permanent magnet synchronous motor.
This patent grant is currently assigned to Hyundai Motor Company, Indudstry-University Cooperation Foundation Hanyang University. Invention is credited to Jung Pyo Hong, Sung Il Kim, Hyuck Roul Kwon, Chang Ha Lee, Tae Geun Lee, Jeong Hee Park, Yong Sun Park.
United States Patent |
8,089,190 |
Lee , et al. |
January 3, 2012 |
Rotor for an interior permanent magnet synchronous motor
Abstract
The present invention provides a rotor for an interior permanent
magnet synchronous motor for driving an air blower, in which the
structure of the rotor is suitably modified to reduce magnetic flux
leakage and, at the same time, maximize saliency ratio, thus
improving the performance of the motor.
Inventors: |
Lee; Chang Ha (Gyeonggi-do,
KR), Park; Jeong Hee (Gyeonggi-do, KR),
Park; Yong Sun (Gyeonggi-do, KR), Kwon; Hyuck
Roul (Gyeonggi-do, KR), Hong; Jung Pyo (Seoul,
KR), Kim; Sung Il (Gyeongsangnam-do, KR),
Lee; Tae Geun (Seoul, KR) |
Assignee: |
Hyundai Motor Company (Seoul,
KR)
Indudstry-University Cooperation Foundation Hanyang
University (Seoul, KR)
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Family
ID: |
43464764 |
Appl.
No.: |
12/620,748 |
Filed: |
November 18, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110012464 A1 |
Jan 20, 2011 |
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Foreign Application Priority Data
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Jul 14, 2009 [KR] |
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10-2009-0063773 |
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Current U.S.
Class: |
310/156.53 |
Current CPC
Class: |
H02K
1/276 (20130101) |
Current International
Class: |
H02K
21/12 (20060101) |
Field of
Search: |
;310/156.53,156.14,156.55,156.56,156.57,156.54 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2002-191144 |
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Jul 2002 |
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JP |
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2005-198487 |
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Jul 2005 |
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JP |
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2008-283775 |
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Nov 2008 |
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JP |
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10-2002-0061282 |
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Jul 2002 |
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KR |
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10-2008-0082779 |
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Sep 2008 |
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KR |
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Primary Examiner: Hanh; Nguyen N
Attorney, Agent or Firm: Edwards Wildman Palmer LLP Corless;
Peter F.
Claims
What is claimed is:
1. A rotor for an interior permanent magnet synchronous motor, the
rotor comprising: N-pole and S-pole permanent magnets inserted into
a rotor core in the circumferential direction thereof in a
multilayered manner and arranged to face each other; and a flux
barrier formed in the rotor core between the N-pole and S-pole
permanent magnets, wherein the multilayered N-pole and S-pole
permanent magnets are arranged around a central axis of the rotor
core in the outer circumferential direction thereof at an obtuse
angle, wherein the flux barrier comprises first and second flux
barriers, which are bent toward the outer circumference of the
rotor core from both ends of the innermost and middle permanent
magnets among the multilayered N-pole and S-pole permanent magnets,
and a third flux barrier which extends from an end of the outermost
permanent magnet along the circumferential direction of the rotor
core and is adjacent to the second flux barrier.
2. The rotor for the interior permanent magnet synchronous motor of
claim 1, wherein an auxiliary flux barrier is further provided
between the outer ends of the first and second flux barriers and
the outer end of the rotor core.
3. The rotor for the interior permanent magnet synchronous motor of
claim 2, wherein a third rib which forms the same plane as the
rotor core is further formed between the inner end of the auxiliary
flux barrier and the outer ends of the second and third flux
barriers and between the outer end of the auxiliary flux barrier
and the outer end of the rotor core.
4. The rotor for the interior permanent magnet synchronous motor of
claim 1, wherein a first rib which divides the N-pole and S-pole
permanent magnets into two equal parts and forms the same plane as
the rotor core is formed in the central region of each of the
N-pole and S-pole permanent magnets.
5. The rotor for the interior permanent magnet synchronous motor of
claim 1, wherein a second rib which forms the same plane as the
rotor core is further formed between both ends of the N-pole and
S-pole permanent magnets and the first to third flux barriers.
6. The rotor for the interior permanent magnet synchronous motor of
claim 1, wherein a residual rotor core surface having a
predetermined thickness is provided between the outermost permanent
magnet among the N-pole and S-pole permanent magnets and the outer
end of the rotor core to serve as a retaining can for protecting
the N-pole and S-pole permanent magnets.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application claims under 35 U.S.C. .sctn.119(a) the benefit of
Korean Patent Application No. 10-2009-0063773 filed Jul. 14, 2009,
the entire contents of which are incorporated herein by
reference.
BACKGROUND
(a) Technical Field
The present disclosure relates, in general, to a rotor for an
interior permanent magnet (IPM) synchronous motor. In particular
preferred embodiments, it relates to a rotor for an interior
permanent magnet (IPM) synchronous motor for driving an air blower,
in which the structure of the rotor is suitably modified to reduce
magnetic flux leakage and, at the same time, maximize saliency
ratio, thus improving the performance of the motor.
(b) Background Art
Rotors of electric motors are generally classified into
surface-mounted permanent magnet (SPM) rotors and interior
permanent magnet (IPM) rotors according to the position of
permanent magnets.
Preferably, the SPM rotors are generally applied to most of
high-speed motors (with a rotor shaft speed of more than 80 m/s)
and, for example, as shown in FIG. 7, a retaining can 2 (or
sleeve), which is a nonmagnetic material, is covered on the surface
of permanent magnets 1 to prevent the permanent magnets from moving
and ensure mechanical safety.
However, the high-speed motor in which the SPM rotor including the
retaining can is applied causes an increase in the magnetic gap.
Therefore, in order to satisfy the power required by the motor, the
number of permanent magnets or coils used increases, or the size of
the motor increases.
Accordingly, multi-layer IPM synchronous motors, in which permanent
magnets are suitably inserted into the rotor in a multilayered
manner, have been studied. However, such structures are rarely
applied to the high-speed motors, and an important reason for this
is that the space utilization for providing the IPM structure is
reduced since the number of poles in the high-speed motors is
limited to less than 4 poles. As a result, the magnetic flux
leakage increases in a rotor core, and thus the efficiency of the
motor decreases. Further, it is not easy to ensure sufficient
mechanical strength against the stress exerted on the rotor core
due to rotational force.
In certain examples where the multi-layer IPM rotor is applied to
the high-speed motor, a space required to ensure mechanical safety,
such as a rib, is increased, which reduces the space utilization
and increases the magnetic flux leakage, thus making it suitably
difficult to ensure the performance of the motor.
For example, as shown in FIG. 6, in a conventional 4-pole interior
permanent magnet rotor, because the whole space of a flux barrier
cannot be filled with a permanent magnet 1, there is a limitation
in the space utilization. Moreover, in order to ensure mechanical
safety during high-speed rotation, it is necessary to increase the
distance between the respective flux barriers 1 and the distance
between both ends of the flux barrier 3 and a rotor core 10, which
corresponds to rib regions 4 and 5. Further, when the rib regions 4
and 5 are increased, the leakage of magnetic flux passing through
the rib regions 4 and 5 increases, and thus it is difficult to
ensure the performance of the motor.
The above information disclosed in this Background section is only
for enhancement of understanding of the background of the invention
and therefore it may contain information that does not form the
prior art that is already known in this country to a person of
ordinary skill in the art.
SUMMARY OF THE DISCLOSURE
In one aspect, the present invention preferably provides a rotor
for an interior permanent magnet (IPM) synchronous motor, in which
permanent magnets are preferably inserted into a rotor core in the
circumferential direction thereof in a multilayered manner to
suitably minimize the force exerted on the rotor core, thus
ensuring sufficient space in a limited area, which can be occupied
by permanent magnets. In further preferred embodiments of the
present invention, a flux barrier is suitably disposed between the
permanent magnets arranged in the circumferential direction of the
rotor core to suitably minimize magnetic flux leakage and suitably
increase saliency ratio to an optimal level.
In a preferred embodiment, the present invention provides a rotor
for an interior permanent magnet synchronous motor, the rotor
preferably including: N-pole and S-pole permanent magnets suitably
inserted into a rotor core in the circumferential direction thereof
in a multilayered manner and arranged to face each other; and a
flux barrier suitably formed in the rotor core between the N-pole
and S-pole permanent magnets, wherein the multilayered N-pole and
S-pole permanent magnets are suitably arranged around a central
axis of the rotor core in the outer circumferential direction
thereof at an obtuse angle.
In another preferred embodiment of the invention, the flux barrier
may include first and second flux barriers, which are suitably bent
toward the outer circumference of the rotor core from both ends of
the innermost and middle permanent magnets among the multilayered
N-pole and S-pole permanent magnets, and a third flux barrier which
extends from an end of the outermost permanent magnet along the
circumferential direction of the rotor core and is suitably
adjacent to the second flux barrier.
In another preferred embodiment, an auxiliary flux barrier may be
further provided between the outer ends of the first and second
flux barriers and the outer end of the rotor core.
In still another preferred embodiment, a first rib which suitably
divides the N-pole and S-pole permanent magnets into two equal
parts and forms the same plane as the rotor core may be suitably
formed in the central region of each of the N-pole and S-pole
permanent magnets.
In yet another preferred embodiment, a second rib which forms the
same plane as the rotor core may be further suitably formed between
both ends of the N-pole and S-pole permanent magnets and the first
to third flux barriers.
In still yet another preferred embodiment, a third rib which forms
the same plane as the rotor core may be further suitably formed
between the inner end of the auxiliary flux barrier and the outer
ends of the second and third flux barriers and between the outer
end of the auxiliary flux barrier and the outer end of the rotor
core.
In a further preferred embodiment, a residual rotor core surface
having a predetermined thickness may be suitably provided between
the outermost permanent magnet among the N-pole and S-pole
permanent magnets and the outer end of the rotor core to serve as a
retaining can for protecting the N-pole and S-pole permanent
magnets.
It is understood that the term "vehicle" or "vehicular" or other
similar term as used herein is inclusive of motor vehicles in
general such as passenger automobiles including sports utility
vehicles (SUV), buses, trucks, various commercial vehicles,
watercraft including a variety of boats and ships, aircraft, and
the like, and includes hybrid vehicles, electric vehicles, plug-in
hybrid electric vehicles, hydrogen-powered vehicles and other
alternative fuel vehicles (e.g. fuels derived from resources other
than petroleum).
As referred to herein, a hybrid vehicle is a vehicle that has two
or more sources of power, for example both gasoline-powered and
electric-powered.
The above features and advantages of the present invention will be
apparent from or are set forth in more detail in the accompanying
drawings, which are incorporated in and form a part of this
specification, and the following Detailed Description, which
together serve to explain by way of example the principles of the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other features of the present invention will now be
described in detail with reference to certain exemplary embodiments
thereof illustrated the accompanying drawings which are given
hereinbelow by way of illustration only, and thus are not
limitative of the present invention, and wherein:
FIG. 1 is a cross-sectional view showing a structure of a rotor for
an interior permanent magnet (IPM) synchronous motor in accordance
with preferred embodiments of the present invention;
FIG. 2 is an enlarged view of FIG. 1;
FIG. 3 is a schematic diagram showing an exemplary basic structure
of an IPM rotor using rectangular permanent magnets in accordance
with Comparative Example 1;
FIG. 4 is a schematic diagram showing an exemplary improved
structure in which a permanent magnet is suitably divided into
several pieces in accordance with Comparative Example 2;
FIG. 5 is a schematic diagram showing an exemplary structure of
permanent magnets of a rotor for an interior permanent magnet (IPM)
synchronous motor in accordance with a preferred Example of the
present invention;
FIG. 6 is a schematic diagram showing an exemplary structure of a
conventional 4-pole IPM rotor; and
FIG. 7 is a schematic diagram showing an exemplary structure of a
conventional surface-mounted permanent magnet (SPM) rotor.
Reference numerals set forth in the Drawings includes reference to
the following elements as further discussed below:
TABLE-US-00001 10: rotor core 12: N-pole permanent magnet 14:
S-pole permanent magnet 16: residual rotor core surface 20: flux
barrier 21: first flux barrier 22: second flux barrier 23: third
flux barrier 24: auxiliary flux barrier 31: first rib 32: second
rib 33: third rib
It should be understood that the appended drawings are not
necessarily to scale, presenting a somewhat simplified
representation of various preferred features illustrative of the
basic principles of the invention. The specific design features of
the present invention as disclosed herein, including, for example,
specific dimensions, orientations, locations, and shapes will be
determined in part by the particular intended application and use
environment.
In the figures, reference numbers refer to the same or equivalent
parts of the present invention throughout the several figures of
the drawing.
DETAILED DESCRIPTION
In one aspect, the present invention features a rotor for an
interior permanent magnet synchronous motor, the rotor comprising
N-pole and S-pole permanent magnets; and a flux barrier, wherein
the N-pole and S-pole permanent magnets are arranged around a
central axis of the rotor core.
In one embodiment, the N-pole and S-pole permanent magnets are
inserted into the rotor core in a circumferential direction.
In another embodiment, the magnets are inserted in a multilayered
manner and arranged to face each other.
In another further embodiment, the flux barrier is formed in the
rotor core between the N-pole and S-pole permanent magnets.
In still another embodiment, the N-pole and S-pole permanent
magnets are arranged around a central axis of the rotor core in an
outer circumferential direction.
In a related embodiment, the magnets are further arranged at an
obtuse angle.
Hereinafter reference will now be made in detail to various
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings and described below. While
the invention will be described in conjunction with exemplary
embodiments, it will be understood that present description is not
intended to limit the invention to those exemplary embodiments. On
the contrary, the invention is intended to cover not only the
exemplary embodiments, but also various alternatives,
modifications, equivalents and other embodiments, which may be
included within the spirit and scope of the invention as defined by
the appended claims.
FIG. 1 is a cross-sectional view showing a structure of a rotor for
an interior permanent magnet (IPM) synchronous motor in accordance
with preferred embodiments of the present invention, and FIG. 2 is
an enlarged view of FIG. 1.
The present invention aims at providing an improved structure of a
rotor for an interior permanent magnet (IPM) synchronous motor in
which permanent magnets are suitably inserted into a rotor core of
the IPM synchronous motor in the circumferential direction or the
rotor core in a multilayered manner to reduce the stress exerted on
the rotor core and, at the same time, rib regions are suitably
minimized to reduce magnetic flux leakage, suitably increase space
utilization, and suitably maximize the saliency ratio, thus
improving the performance of the motor.
In further preferred embodiments, the present invention provides an
improved structure in which the amount of permanent magnets used is
minimized, the maximum stress suitably exerted on the rotor is
reduced, and the structural safety is suitably ensured by
appropriately arranging the permanent magnets and flux barriers in
the rotor core, thus suitably maximizing the performance of the
motor.
According to further preferred embodiments, for this purpose, as
shown in FIGS. 1 and 2, N-pole and S-pole permanent magnets 12 and
14 are suitably inserted in a rotor core 10 in the circumferential
direction thereof in a multilayered manner (more than three layers)
and suitably arranged to face each other, and a flux barrier 20 is
suitably formed on the surface of the rotor core 10 between the
N-pole and S-pole permanent magnets 12 and 14.
Preferably, in more detail, the multilayered (more than three
layers) N-pole and S-pole permanent magnets 12 and 14 are suitably
arranged around a central axis of the rotor core 10 in the outer
circumferential direction thereof at an obtuse angle and at regular
intervals such that the force of the permanent magnets 12 and 14 is
suitably uniformly dispersed on the entire surface of the rotor
core 10, thus suitably reducing stress concentration.
Preferably, the flux barrier 20 may suitably include first to third
flux barriers 21 to 23. The first and second flux barriers 21 and
22 are suitably bent toward the outer circumference of the rotor
core 10 from both ends of the innermost and middle permanent
magnets among the multilayered N-pole and S-pole permanent magnets
12 and 14. In further preferred embodiments, the third flux barrier
23 suitably extends from an end of the outermost permanent magnet
along the circumferential direction of the rotor core 10 and is
suitably adjacent to the second flux barrier 22.
Preferably, an auxiliary flux barrier 24 may be further provided
between the outer ends of the first and second flux barriers 21 and
22 and the outer end of the rotor core 10 in the circumferential
direction of the rotor core 10.
In further preferred embodiments, with the first to third flux
barriers 21 to 23 suitably disposed in the rotor core 10, it is
possible to suitably prevent the magnetic flux from leaking and,
especially, the space in which the first to third flux barriers 21
to 23 is formed can be utilized as a space for installing permanent
magnets, if necessary.
With the auxiliary flux barrier 24, it is possible to suitably
disperse the stress concentration and suitably minimize the
magnetic flux leakage.
Accordingly, since the flux barrier 20 limits q-axis magnetic flux
and serves as a passage of d-axis magnetic flux, it suitably
increases the saliency ratio and suitably reduces mechanical
strength. However, according to the present invention, the flux
barrier 20 is suitably divided into the first to third flux
barriers 21 to 23 and the auxiliary flux barrier 24 and their
arrangement is suitably optimized to prevent the saliency ratio
from increasing to a critical level and maintain the mechanical
strength at a constant level.
According to further preferred embodiments of the present
invention, the central region of each of the N-pole and S-pole
permanent magnets 12 and 14 is preferably divided into two equal
parts in the radial direction, and the divided region serves as a
first rib 31 which forms the same plane as the rotor core 10.
Accordingly, since the permanent magnets 12 and 14 arranged in the
circumferential direction of the rotor core 10 are bisected by the
first rib 31, it is possible to suitably disperse the maximum
stress exerted on a permanent magnet formed as a single body.
According to further embodiments, preferably, a second rib 32 which
forms the same plane as the rotor core 10 may be suitably disposed
between both ends of the N-pole and S-pole permanent magnets 12 and
14 and the first to third flux barriers 21 to 23 such that both
ends of the N-pole and S-pole permanent magnets 12 and 14 and the
first to third flux barriers 21 to 23 are separated from each
other.
In further embodiments of the invention, more preferably, a third
rib 33 which forms the same plane as the rotor core 10 may be
further suitably disposed between the inner end of the auxiliary
flux barrier 24 and the outer ends of the second and third flux
barriers 22 and 23 and between the outer end of the auxiliary flux
barrier 24 and the outer end of the rotor core 10.
Further, it is reported that the thus formed first to third ribs 31
to 33 serve to suitably maintain the shape of the rotor and
increase the saliency ratio by reducing the thickness thereof.
Accordingly, it is possible to suitably reduce the magnetic flux
leakage and improve the saliency ratio by suitably reducing the
thickness of the first to third ribs 31 to 33 formed in the rotor
core 10 in accordance with the present invention, thus improving
the performance of the motor.
In further preferred embodiments of the present invention, a
residual rotor core surface 16 having a predetermined thickness may
be suitably provided between the outermost permanent magnet among
the N-pole and S-pole permanent magnets 12 and 14 and the outer end
of the rotor core 10 to serve as a retaining can for protecting the
N-pole and S-pole permanent magnets 12 and 14.
In certain exemplary embodiments, a test was performed using a
predetermined program to suitably analyze the maximum stress, the
amount of permanent magnets used, the flux linkage per phase, the
saliency ratio, and the generated torque by modeling the
arrangement of the N-pole and S-pole permanent magnets in the
circumferential direction.
According to preferred embodiments of the invention and as shown in
FIG. 3, FIG. 3 is a schematic diagram showing an exemplary basic
structure of an IPM rotor using rectangular permanent magnets in
accordance with Comparative Example 1, According to other preferred
embodiment, and as shown in FIG. 4, FIG. 4 is a schematic diagram
showing an improved structure in which a permanent magnet is
divided into several pieces in accordance with Comparative Example
2, and FIG. 5 is a schematic diagram showing an exemplary structure
of permanent magnets of a rotor for an interior permanent magnet
(IPM) synchronous motor in accordance with a preferred Example of
the present invention.
The test results of the maximum stress, the amount of permanent
magnets used, the flux linkage per phase, the saliency ratio, and
the generated torque are shown in the following Table 1:
TABLE-US-00002 TABLE 1 Flux Maximum Amount of linkage Saliency
Generated Analysis stress PMs used per phase ratio torque model
(MPa) (mm.sup.2) (Wb) (Lq/Ld) (Nm) Comparative 241.9 126.6 0.0152
1.11 0.96 Example 1 Comparative 111.4 151.4 0.0156 1.42 0.15
Example 2 Example 157.5 146.2 0.0186 2.17 1.96
As shown in Table 1, in Comparative Example 1, the flux linkage or
torque was considerably low. In Comparative Example 2, the maximum
stress could be considerably reduced by dividing the permanent
magnet into several pieces, but the amount of permanent magnets
used was suitably increased. Whereas, in the Example of the present
invention, it was possible to suitably reduce the amount of
permanent magnets used, suitably increase the flux linkage and the
saliency ratio, and further improve the performance of the motor
through an additional increase in torque.
As described above, the present invention provides, but is not
limited to, the following effects.
According to the rotor for the IPM synchronous motor in accordance
with preferred embodiments of the present invention, the permanent
magnets are suitably inserted into the rotor core in the
circumferential direction thereof in a multilayered manner to
suitably minimize the force exerted on the rotor core, thus
ensuring sufficient space in a limited area, which can be suitably
occupied by the permanent magnets. In further preferred
embodiments, the flux barriers are suitably disposed between the
permanent magnets arranged in the circumferential direction of the
rotor core to suitably minimize magnetic flux leakage, and, in
further preferred embodiments, the plurality of ribs are also
suitably disposed between the permanent magnets and between the
flux barriers to suitably provide mechanical strength for
maintaining the shape of the rotor.
The invention has been described in detail with reference to
preferred embodiments thereof. However, it will be appreciated by
those skilled in the art that changes may be made in these
embodiments without departing from the principles and spirit of the
invention, the scope of which is defined in the appended claims and
their equivalents.
* * * * *